Ribbon cables comprise a planar array of parallel stranded wires imbedded in an integral array of insulation. The insulation is disposed to surround each stranded wire and to integrally fill the webs between adjacent wires. The opposed surfaces of a ribbon cable are characterized by distinct parallel ribs defined by the wires in the insulation. In this regard it should be noted that ribbon cable is a term of art defining a product distinct from flat flexible cable (FFC). FFC generally is much thinner, includes flat conductive strips as opposed to round stranded wire, has thinner insulation and no external ribs. FFC's generally are used in lower current applications and in environment less likely to be subjected to direct pulling forces.
Ribbon cables are terminated to electrical connectors having housings with electrically conductive terminals therein. Each terminal typically is stamped and formed from a unitary piece of metallic material. The terminals are mounted in the housing with a pitch or spacing generally corresponding to the spacing between the stranded wires in the ribbon cable.
It is desirable to automate the termination of cables as much as possible. Insulation displacement terminals are widely employed and are well suited to automated termination processes. The typical prior art insulation displacement terminal includes at least one blade defining an insulation displacement slot. The blade is disposed on the terminal such that the plane of the blade extends transverse to the axis of the wires in the ribbon cable. The wire, and the insulation immediately surrounding the wire, may be urged into the insulation displacement slot, such that the blade pierces through the insulation and electrically contacts the wire in the cable. The dimensions of the insulation displacement slot are selected to achieve a high quality electrical connection with the stranded wire conductor in the ribbon cable.
It is also necessary to ensure that strain relief is achieved between the ribbon cable and the electrical connector. More particularly, the ribbon cables leading to many electrical connectors often are subjected to pulling forces. If the pulling force exerted on the cable is transmitted directly to the insulation displacement portions of the terminal, the quality of the electrical connection can be degraded and/or conductors in the stranded wire of the ribbon cable may be severed.
Strain relief structure has been employed in the prior art to securely affix the insulation of the ribbon cable to a portion of the connector that does not perform a terminating function. For example, some connectors include strain relief structure on the housing for clamping into engagement with the ribbon cable. These structures often require separate costly parts and/or complex molds. Furthermore, these structures generally require separate manual actuation after the termination is completed and after the terminals are inserted into the electrical connector housing. Connectors that employ discrete insulated wires as opposed to ribbon cables often employ arrays of crimpable arms for secure crimped engagement with the insulation on each discrete wire. The crimped engagement of the terminal with the insulation on the wire generally will provide adequate strain relief. Similar strain relief structure is provided on terminals for flat flexible cables. For example, U.S. Pat. No. 4,371,225 issued to Narozny on Feb. 1, 1983 and shows a terminal with pairs of opposed parallel pointed arms for piercing entirely through the insulation and flat conductor of the FFC. The arms are then folded over to simultaneously achieve both electrical termination and strain relief. This teaching for FFC's is not directly applicable to ribbon cables because of the different termination structures required for the round stranded wires of ribbon cables and the likelihood of greater pull-out forces imposed on ribbon cables.
Attempts have been employed to employ the crimped strain in relief teaching of discrete wires or FFC's on ribbon cables. For example, the prior art has prepared the end of the ribbon cable to be terminated by punching, cutting or otherwise removing webs of insulation between adjacent conductors to be terminated. Strain relief crimpable arms may then be passed through the slots in the ribbon cable and crimped into engagement with portions of the insulation surrounding the associated conductor. Connectors employing this prior art technology may perform well, but require a costly and time consuming additional step in the manufacturing process to form the slots adjacent the end of the ribbon cable.
In view of the above, it is an object of the subject invention to provide a terminal for achieving a high quality electrical connection with strain relief to a ribbon cable.
Another object of the subject invention is to provide an insulation displacement terminal for strain relief connection to a ribbon cable.
A further object of the subject invention is to provide an insulation displacement terminal for a ribbon cable with crimpable strain relief structure for piercing the insulation between adjacent conductors of a ribbon cable.
An additional object of the subject invention is to provide an insulation displacement terminal for ribbon cables with support for insulation displacement structure.